This invention relates to an electronic control fuel injection system for electronically controlling the amount of fuel to be supplied through an injection valve into an engine.
The use of an electronic control fuel injection system for an engine to control the emission of harmful constituents of exhaust gases, as well as to reduce fuel consumption by interrupting the supply of fuel to an engine while the engine remains in a decelerating condition is known. When the supply of fuel is interrupted, fuel droplets, which normally cling to the inner surfaces of an intake system, e.g., an intake port and the like, before the interruption of the fuel supply, are delivered to a combustion chamber and are consumed therein. If the interruption in the fuel supply is considerably long, then the inner surfaces of an intake port and the like are dried to the extent that no fuel droplets are present. In addition, the interruption of the supply of fuel causes residual gases to be completely scavenged by air from a combustion chamber in an engine, and hence no residual remains in the combustion chamber. Meanwhile, when an engine is accelerated again after a long interruption in the fuel supply, an injection valve is operated by the control-signal-generating circuit which determines the optimum opening duration of an injection valve in accordance with the operational parameters of an engine, so that an optimum amount of fuel is injected through the injection valve into an engine. However, when this occurs, the amount of fuel thus injected is insufficient to afford a mixture charge of a desired air-fuel ratio called for by the control-signal-generating circuit, because of the lack or absence of a sufficient amount of fuel droplets which normally reside in and coat an intake pipe and the like. Thus, fuel is not always supplied in its entirety to a combustion chamber, but part of the fuel of a given amount is consumed so as to wet or moisten the inner surfaces of an intake system. As a result, the air-fuel ratio of a mixture charge in a cylinder upon acceleration, following a long duration of the interrupted fuel supply, remains, for the duration of several cycles of an engine, at a value higher than a given value (a lean mixture), so that the engine is likely to misfire. Also, when an air-fuel ratio of a mixture charge in a cylinder reaches a level which allows for ignition, a sharp rise in torque is produced in the engine, at the time of subsequent acceleration, so that an undesirable shock is imposed on an automobile. .